Replaced fuel sender in aux tank on 2003 330 Express

[everwhom]

My fuel sender went bad on my 2003 330 Express AUX tank. I was originally going to have my marina replace it as I felt that I didn't want to mess with the fuel tank, but it turns out it was a very easy DIY job. A quick email to Grady let me know that my AUX sender is 26.5" while the main tank is 25" - since KUS/Wema doesn't sell 1/2" increments I purchased a 26" SSS/SSL Sender directly from https://kus-usa.com/ plus the Viton gasket kit.

Installation couldn't have been easier -- there was some corrosion / crud under the old seal, so I just used some WD40 on a rag to dissolve it plus some fingernail scraping being careful not to let debris fall into the tank. The original sender (I assume from the factory) used standard quick-connects, but interestingly they were not the heat-shrink crimps. I stayed with the same so I wouldn't have to use an open flame or heat gun right on top of the fuel tank!

If you do it yourself, definitely read the instructions in advance and make sure to mark or note the orientation of the original sender before you remove -- the new one has to maintain the same orientation. Also weirdly the black wire is the signal wire and the pink wire is ground!

 

[PDX-Boats]

Thanks for the post. I've considered upgrading mine to NMEA 2000 pressure sensors (made for the fuel tanks).
Haven't pulled the trigger yet though.

 

[seasick]

My fuel sender went bad on my 2003 330 Express AUX tank. I was originally going to have my marina replace it as I felt that I didn't want to mess with the fuel tank, but it turns out it was a very easy DIY job. A quick email to Grady let me know that my AUX sender is 26.5" while the main tank is 25" - since KUS/Wema doesn't sell 1/2" increments I purchased a 26" SSS/SSL Sender directly from https://kus-usa.com/ plus the Viton gasket kit.

Installation couldn't have been easier -- there was some corrosion / crud under the old seal, so I just used some WD40 on a rag to dissolve it plus some fingernail scraping being careful not to let debris fall into the tank. The original sender (I assume from the factory) used standard quick-connects, but interestingly they were not the heat-shrink crimps. I stayed with the same so I wouldn't have to use an open flame or heat gun right on top of the fuel tank!

If you do it yourself, definitely read the instructions in advance and make sure to mark or note the orientation of the original sender before you remove -- the new one has to maintain the same orientation. Also weirdly the black wire is the signal wire and the pink wire is ground!

Are you sure that the signal is the black? That is 100% reversed from the specs. Hmmmm
Is there a ground wire attached directly to the metal tank? If so is it Teed off to the pink wire?

 

[everwhom]

Are you sure that the signal is the black? That is 100% reversed from the specs. Hmmmm
Is there a ground wire attached directly to the metal tank? If so is it Teed off to the pink wire?

Yeah - I had to read that at least 5 times to make sure I wasn't missing something:
This is from the PDF you can download at https://kus-usa.com/wp-content/uploads/2020/02/KUS-USA_SendingUnit_Installation_v4.pdf

PROPER WIRING INSTALLATION:
- Connect ground (pink) wire from the KUS sending unit to a common grounding hook-up.
- Connect (black) wire from the KUS sending unit to gauge hook-up. If your gauge has color coded hook-ups, maintain this
coding as you connect the sender and ground wires.

Yes, on my 330, there's a female spade connector that is T'd to the ground tank wire (just 6 inches away) and to the wire that presumably runs back to the gauge. This is where the pink wire from the sender plugs into!

 

[seasick]

I will have to check my wiring next time I get to the boat. I know it has a WEMA sender since I just replaced the fuel lines to the motor.
It seems that unlike older style senders that have a spade lug directly connected to the sender signal and a spade plug connected to the flange for ground, the KUS must have two wires that are isolated from the flange completely. In that case, it wouldn't make a difference in how the two wires are connected. To prove that, all you would have to do is unplug the sender pink connection ( that is currently grounded) and see if the gauge reads empty.
I guess you learn something new every day.

 

[everwhom]

Interesting followup: after replacing the sender, my gauge was reading 85% when the tank was full. After first thinking this was a calibration issue, I discovered that the sender was showing the correct resistance value (about 30 ohms at full) and that my gauge (Yamaha Command Link Plus, version 1) doesn't have calibration for the fuel sender.

I traced the problem to corrosion at the disconnect connectors and wire. Basically instead of connecting the sender wires with heat shrink butt connectors, Grady (I assume) used spade disconnects... I solved the problem by cutting back the wire which was still corroded a fair amount back under the insulation, sanding off the corrosion and recrimping new connectors + liquid electrical tape. I didn't use heat shrink because I didn't like the idea of using an open flame 3 inches above the gas tank! Voila - now the gauge reads correctly!

Interesting that the American standard for fuel senders is that full is low resistance and empty is high, whereas the European standard is reversed. So corrosion at the connectors (a common problem) will result in thinking you have less fuel than you have which might be inconvenient, whereas the Europe you might be tricked into thinking you have more than you have which could be fatal.

 

[SkunkBoat]

I need to spend some time on my fuel gauge/senders. Gauges appear to top out 20 gals before the tanks top out and half tank readings are about 40 gals on 125 gl tanks. Dunno if 265 tanks are v shaped which would provide some cause but not the topping out problem.

PO ran a new pink wire for the aux tank for some reason. The main tank uses the Grady wiring.
I also have problems if I don't have an extra ground connecting tanks together and to neg battery.

My tanks were replaced by PO in 2017 and they have threaded KUS senders that I assume are the correct depth. I like the threaded tank/senders...no screws or gasket...

Funny thing, I changed my dash config and disconnected and moved my zuke gauges. Gauge settings reside in the port gauge but i reversed them and fuel gauge did not work. To clarify, the gauges are identical but the gauge that plugs into the unmarked plug (port) stored the gauge setup for "tank 1 & 2". There are other plugs marked stbd and center. I reversed them and the gauge was set to europe by default. Quite confusing...I still might not know exactly what I'm talking about....

maybe this pink & black thing is messing with me?

 

[seasick]

Interesting followup: after replacing the sender, my gauge was reading 85% when the tank was full. After first thinking this was a calibration issue, I discovered that the sender was showing the correct resistance value (about 30 ohms at full) and that my gauge (Yamaha Command Link Plus, version 1) doesn't have calibration for the fuel sender.

I traced the problem to corrosion at the disconnect connectors and wire. Basically instead of connecting the sender wires with heat shrink butt connectors, Grady (I assume) used spade disconnects... I solved the problem by cutting back the wire which was still corroded a fair amount back under the insulation, sanding off the corrosion and recrimping new connectors + liquid electrical tape. I didn't use heat shrink because I didn't like the idea of using an open flame 3 inches above the gas tank! Voila - now the gauge reads correctly!

Interesting that the American standard for fuel senders is that full is low resistance and empty is high, whereas the European standard is reversed. So corrosion at the connectors (a common problem) will result in thinking you have less fuel than you have which might be inconvenient, whereas the Europe you might be tricked into thinking you have more than you have which could be fatal.

It's the glass half empty - half full scenario.

 

[everwhom]

I need to spend some time on my fuel gauge/senders. Gauges appear to top out 20 gals before the tanks top out and half tank readings are about 40 gals on 125 gl tanks. Dunno if 265 tanks are v shaped which would provide some cause but not the topping out problem.

If you can easily disconnect the senders entirely, you might try using a multimeter to measure the resistance at full or any other known level. When full it should read 30 ohms and empty should be 240 ohms. 1/2 tank should be about 135. Note you can only measure this when the sender is completely disconnected from any other wiring.